Abstract:
The present work deals with the studies carried out on the development, optimization and validation of RP-HPLC and HPTLC methods for the simultaneous estimation of Telmisartan and Ramipril in combined dosage form. Market is folded with combination of drugs in various dosage forms. The multi-components formulations have gained a lot of importance now days due to greater patient acceptability, increased potency, multiple action, fewer side effects and quicker reliefs. For simultaneous estimation of drugs present in multi-component dosage form, High Pressure Liquid Chromatography (HPLC) and High Pressure Thin Layer Chromatography (HPTLC) methods are considered to be most suitable since it is extremely precise, accurate, sensitive, linear and rapid. The literature survey carried out and it revealed that several analytical methods have been reported for estimation of these drugs as individual or in combination with other drugs. So the objective of the work is to develop HPLC and HPTLC methods for simultaneous estimation of drugs in multi-component dosage form for which no analytical method has been previously reported. Hence, present study have been planned to develop a specific, precise, accurate, linear, simple and rapid HPLC and HPTLC methods for simultaneous estimation of Telmisartan and Ramipril in tablet dosage form.

REFERENCE ID: PHARMATUTOR-ART-1138

Introduction:
The present work deals with the studies carried out on the development, optimization and validation of RP-HPLC and HPTLC methods for the simultaneous estimation of Telmisartan and Ramipril in combined dosage form.

Market is folded with combination of drugs in various dosage forms. The multi-components formulations have gained a lot of importance now a day due to greater patient acceptability, increased potency, multiple action, fewer side effects and quicker relief.

Classification of Instrumental Methods of Analysis9-11Most of the instrumental techniques fit in to one of the three principal areas such as

Ø Spectroscopy

Ø Electrochemistry

Ø Chromatography

Spectroscopy
Spectroscopy is the measurement and interpretation of electromagnetic radiation absorbed, scattered, or emitted by atoms, molecules or other chemical species.

Electrochemistry
In this, each basic electrical measurement of current like resistance and voltage has been measured alone or in combination for analytical purposes. Examples: Potentiometry, Voltametric Techniques, Amperometric Techniques, Electrogravimetry and Conductance Techniques

CHROMATOGRAPHY
The term ‘Chromatography’ covers those processes aimed at the separation of the various species of a mixture on the basis of their distribution characteristics between a stationary and a mobile phase. Chromatographic methods can be classified most practically according to the stationary and mobile phases, as shown in the following table

Modes of Chromatography
Modes of chromatography are defined essentially according to the nature of the interactions between the solute and the stationary phase, which may arise from hydrogen bonding, Vander walls forces, electrostatic forces or hydrophobic forces or basing on the size of the particles (e.g. Size exclusion chromatography).

Different modes of chromatography are as follows:

· Normal Phase Chromatography

· Reversed Phase Chromatography

· Reversed Phase – ion pair Chromatography

· Ion Chromatography

· Ion-Exchange Chromatography

· Affinity Chromatography

· Size Exclusion Chromatography

Adsorption chromatography or normal phase chromatography
In normal phase chromatography, the stationary phase is a polar adsorbent and the mobile phase is generally a mixture of non-aqueous solvents.

The silica structure is saturated with silanol groups at the end. These OH groups are statistically disturbed over the whole of the surface. The silanol groups represent the active sites (very polar) in the stationary phase. This forms a weak type of bond with any molecule in the vicinity when any of the following interactions are present.

® Dipole-induced dipole,

® Dipole-dipole,

® Hydrogen bonding,

® p-Complex bonding,

These situations arise when the molecule has one or several atoms with lone pair electron or a double bond. The absorption strengths and hence k’ values (elution series) increase in the following order. Saturated hydrocarbons < olefins < aromatics < organic halogen compounds < sulphides < ethers< esters < aldehydes and ketones < amines < sulphones < amides < carboxylic acids. The strength of interactions depends not only on the functional groups in the sample molecule but also on steric factors. If a molecule has several functional groups, then the most polar one determines the reaction properties.

Chemically modified silica, such as the aminopropyl, cyanopropyl and diol phases is useful alternatives to silica gel as stationary phase in normal phase chromatography.

The aminopropyl and cyanopropyl phases provide opportunities for specific interactions between the analyte and the stationary phases and thus offer additional options for the optimizations of separations. Other advantages of bonded phases lie in their increased homogeneity of the phase surface.

Reversed Phase Chromatography
In 1960’s chromatographers started modifying the polar nature of silanol group by chemically reacting silica with organic silanes. The objective was to make less polar or non polar, so that polar solvents can be used to separate water-soluble polar compounds. Since the ionic nature of the chemically modified silica is now reversed i.e. it is non-polar or the nature of the phase is reversed. The chromatographic separation carried out with such silica is referred to as reversed- phase chromatography. The retention of the compounds decreases in the following order: aliphatics > induced dipoles (i.e. CCl4) > permanent dipoles (e.g.CHCl3) > weak lewis bases (ethers, aldehydes, ketones) > strong lewis bases (amines) > weak lewis acids (alcohols, phenols) > strong lewis acids (carboxylic acids). Also the retention increases as the number of carbon atoms increases.